INVESTMENT OPERATIONS - Schedule of Available-for-Sale Credit Losses on Fixed Maturities Held by the Company for Which a Portion of Other-than-Temporary Impairments were Recognized in Other Comprehensive Income (Loss) (Details) - Fixed maturities - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Roll Forward]
Beginning balance	$ 12,685	$ 22,761
Additions for newly impaired securities	0	2,092
Additions for previously impaired securities	0	525
Reductions for previously impaired securities due to a change in expected cash flows	(12,685)	(22,759)
Reductions for previously impaired securities that were sold in the current period	0	0
Ending balance	$ 0	$ 2,619